Electromagnetic chuck



Nov. 1,1927. 1,647,951

r J. BING ELECTROIAGNETIC CHUCK;

Filed Dec. 11, 1924 9 9 5 J5 y T 4 a 1 12 a a J fa If 2090 for MZLG Z Patented Nov. 1, 1927.

UNITED STATES PATENT OFFICE.

JULIUS DING, 0F EISENACH, GERMANY, ASSIGNOR TO MAGNET-WEEK G. M. B. H. EISENACH, SPEZIALFAIBRIK FUR ELEKTBOMAGNET-APPARATE, OF EISENACH,

THURINGIA, GERMANY.

ELECTROMAGNETIC CHUCK.

Application filed December 11, 1924, Serial No. 755,289, and in Germany December 17, 1923.

My inventionrelates to improvements in electromagnetic chucks. Electromagnetic chucks, such as are now in use comprise a ma' etic body in the form of a box covered at its top by a magnetic field pole and enclosing a system of electric coils having a supply of direct current, the field pole being in the form of a plate composed of individual magnetic bodies separated from one another by non-magnetic material, and the coils being so connected to the source of electric energy that field poles of different polarities are alternately produced on the said plate. In order to cause a large proportion of the lines of force to pass from the alternating poles through the blank to be fixed to the chuck the poles are separated by non-magnetic matter, ordinarily nonmagnetic metals, such as brass, zinc etc., said non-magnetic material having in addition the function to close the inner parts of the magnetic body as against the access of liquid. By thus magnetically separating the zones of different polarity the lines of force are caused to pass through the blanks placed on the chuck so that the said blanks are firmly held on the chuck.

Constructions of this type, such as are now in use, are objectionable for the reason that the liquid used for cooling the blanks being worked gradually passes between the field poles and the magnetic body and between the sections of the plate of field poles into the inner part of the magnetic body, where it injures the exciting coils by shortcircuiting the same. Further, only a part of the surface of the magnetic plate is made use of for directing lines of force through the blanks and for fixing the same in position, the non-magnetic parts of the plate being inoperative. Finally the cost of the manufacture of the said subdivided field plate is high.

The object of the improvements is to pr vide an electro-magnetic chuck in which the said objections are obviated, and with this object in view I construct the active part of the top plate of the chuck exclusively from magnetic material, said plate being comparatively thin, so that when properly arranging the magnetic fields a suflicient proportion'of the lines of force passes through the blanks for holding the same in position. Further, I construct the member supporting the blanks from a solid plate which is preferably made integral with the body of the magnetic casing, so that there is no scam in the magnetic body through which the liquid might have access to the coils.

For the purpose of explaining the invention an example embodying the same has been shown in the accompanying drawing in WlllCll the same reference characters have been used in all the views to indicate correspond'ing parts. In said drawing,

Fig. 1, is a top-plan view of the chuck, and Fig. 2,'i-s a sectional elevation taken on the line 2-2 of Fig. 1.

In the example shown in the drawingtheelectromagnetic chuck comprises a box or easing made from a suitablemagnetic material, such as cast steel, said box being secured with its open bottom to a bottom plate 2 which is likewise made from magnetic ma te'rial. As shown the casing 1 issecured-to the bottom plate 2 by meansof screws2 The casing comprises a top plate 3,,a cylin-.

drical side wall 4, annular concentric walls 5 and 6 disposed within the box and a suitable distance away from the side wall 4 and from each other, and an axial core 7, said side wall, annular walls and core being made integral with the top plate 3.

The annular chambers 8, 8? and 8" pro-v vided between the said walls and the core cated'by the arroww, so that the core part 7 and the inner annular portions 5 and 6 and the portions of the top plate adjacent thereto have the same polarity, which may be for example positive polarity, while the side wall 4 and the adjacent portions of the plate 3 have the opposite or negative polarity.

The annular wall 5 is made thicker than the side wall 4, and the annular member 6 is made thicker than the annular member 5, and the top plate 3 is comparatively thin. In the preferred construction the thickness plate 2 may be of the top plate is less than that of the side wall 4. In no case is the section 14: of the plate 3 which is perpendicular to the radial lines of force larger than the largest crosssection of the side wall 4. The bottom plate 2 is made comparatively thick in order to reduce as far as possible the magnetic resistance thereof. Near the bottom parts the walls 4, 5, 6 and the core 7 are provided with bores or passages 12 connecting the chambers of the casing with one another and with the outer air. Further, the bottom made with two bores 13. Through the said passages or bores the outer air has access to the inner part: of the chuck, and any humidity collected within the chuck may escape through the said bores.

Experience has shown that in a chuck of the construction described above blanks of magnetic material are sufiiciently fixed to the plate 3 at any part thereof, and 1t is not necessary to supply very high current to the exciting coils.

I wish it to be understood that my invention is. not limited to the construction or type of the chuck shown in the drawing. An important feature of the new construction is that the apparatus is perfectly water-proof the coils being covered at their top by a metallic body having no seams whatever. Further, I do not limit myself to connecting the coils to the source of electric energy in the manner described above in which the same polarity is produced at the median part of the plate 3. In such cases in which sections of different polarity are alternately produced on the plate I prefer to provide a very thin top plate 3.

I claim:

1. An electromagnetic chuck, comprising a casing having a side wall and a top plate made integral therewith. and having two parts of opposite magnetic polarities, one of said parts comprising the main central portion of said plate, the other one comprising the small marginal portion of said plate.

2. An electromagnetic chuck, comprising a magnetic casing having a top plate adapted to ave blanks of magnetic material placed thereon, a side wall made integral with said top plate, and a bottom plate removably connected with said side wall, and an electric coil within said casing, said top plate having only two zones of different polarities and both of largely different area.

3. An electromagnetic chuck, comprising a magnetic frame substantially circular in form and having a plate of a material substantially magnetically homogenous in radial direction and substantially uniform in thickness, and magnetizing means for said frame adapted to produce a magnetic polarity of similar character all over the main portion of said plate.

4. An electromagnetic chuck, comprising a casing of magnetic material substantially circular inform and having a plate of substantially uniform thickness and thinner than the side wall of said casing, means to bridge the said side wall at the margin away from said plate, and electric energizing means within said casing adapted to produce a magnetic polarity of similar character all over the main portion of said plate.

5. An electromagnetic chuck, comprising a magnetic frame having a plate made integral therewith and of a material substantially magnetically homogeneous in radial direction and substantially uniform in thickness, and magnetizing means for said frame.

6. An electromagnetic chuck comprising a plate of magnetic material adapted to have blanks of magnetic material placed thereon, a side wall of magnetic material made integral with said plate, magnetic bridging means at the end of the side wall opposite to said plate, and electromagnetic means for magnetizing said plate, said electromagnetic means comprising an axial core and a concentric wall magnetically connecting said plate and bridging means and electric coils respectively disposed between said core and concentric wall and said concentric wall and side wall and means for energizing said coils so as to produce equal olarities in the said core and concentric wa l.

7. An electromagnetic chuck comprising a plate of magnetic material adapted to have blanks of magnetic material placed thereon,

a side wall of magnetic material made in with said plate, magnetic bridging tegral means at the end of the side wall opposite to said plate, and electromagnetic means for magnetizing said plate, said electromagnetic means comprising an axial core and a plurality of concentric annular cores magnetically connectin said plate and brid ing means and e ectric coils within tfie spaces provided between the axial core, the annular cores and the side wall, and means for supplying electric current to said coils in a direction for producing equal polarities in all of said cores.

8. An electromagnetic chuck, comprising a pair of spaced members substantially in the form of plates, 9. side wall of magnetic material forming a closed casing with said members, a plurality of ring shaped concentrio core pieces internally of said side wall magnetically connecting said members, and means for magnetizing said side wall and core pieces so that the polarity of said side wall is different from that of all of said' core pieces.

9. In an electromagnetic chuck, the combination, with a casing of magnetic material comprising a top plate, an outer core of magnetic material made integral with said top plate, a bottom plate of magnetic material secured to said outer core, an axial core magnetically connecting said top and bottom plates, and a core intermediate said axial core and outer core magnetically connecting said top and bottom plates, of electric means for ma netizing said cores arranged so that two acfi'acent cores have similar polarity.

10. In an electromagnetic chuck, the combination, with a casing of magnetic material comprising a top plate, an outer core of magnetic material made integral with said top plate, a bottom plate of magnetic material secured to said outer core, an axial core magnetically connecting said top and bottom plates, and cores intermediate said axial core and outer core magnetically connecting said top and bottom plates, of electric means for magnetizing said cores arranged so that said axial and intermediate cores have similar polarity.

11. An electromagnetic chuck, comprising a plurality of concentric core members, a side wall, a yoke member magnetically connecting said core members and said side wall,

a pole plate of substantially uniform thickness integral with said core members and said side Wall, and means for producing a similar magnetic polarity within all of said core members and an opposite magnetic polarity within said side wall.

12. An electromagnetic chuck, comprising a body of magnetic material providing a closed magnetic circuit and including a holdgassed through the remainlng part of said dy perpendicular to the lines of force traversing the same, and magnetizing means for said body adapted to produce a magnetic polarity of similar character all over the main portion of said holding plate.

13. An electromagnetic chuck, comprising a casing having a top plate integral therewith, and magnetizing means within said casing adapted to produce a magnetic polarity of similar character all over the main part of said top plate and a magnetic polarity of opposite character in a remaining narrow marginal portion of said plate.

14. An electromagnetic chuck comprising a casing having a side wall, a plurality of core pieces concentric to said side wall and a top plate integral with said side wall and said core pieces and having a small thickness substantially uniform all over its radial extent, and means for producing two zones of different ma netic polarity within said top plate, one 0% said zones having a considerably larger area than the other one.

In testimony whereof I afiix my signature.

JULIUS BING. 

